Nonviral jet injection is an applicable technology for in vivo gene transfer of naked DNA. However, little is known about the biodistribution and clearance of jet-injected DNA, or about its localization within tissue and cells. Therefore, in this study we analyzed the intratumoral and systemic biodistribution of jet-injected naked DNA in human colon carcinoma-bearing NCr-nu/nu mice, which were jet-injected with the pCMV plasmid DNA. Intratumoral and systemic plasmid DNA biodistribution was analyzed 5, 10, 20, and 40 min and 3, 6, 24, 48, and 72 hr after jet injection, using quantitative real-time polymerase chain reaction. In the tumors, a rapid drop in naked DNA load within 24 hr of jet injection was shown. Detailed analysis of intratumoral distribution of rhodamine-labeled DNA revealed the presence of plasmid DNA within tumor cells 5 min after jet injection and further accumulation of significant DNA amounts in the cell nuclei 30 to 60 min after jet injection. In the blood, DNA amounts rapidly dropped within 10 to 40 min of jet injection to less than 0.001 pg of plasmid per 250 ng of tissue DNA and only minimal plasmid DNA dissemination was detected in liver, lung, spleen, kidney, and ovaries, which was cleared 3 to 6 hr after jet injection. By contrast, in heart, bone marrow, and brain almost no plasmid DNA was detectable.
OVERVIEW SUMMARYIn this study jet injection was used for the direct gene transfer of naked DNA into tumors to evaluate the biodistribution of plasmid DNA. The intratumoral plasmid DNA load and the systemic appearance of the DNA was analyzed by quantitative real-time polymerase chain reaction 5, 10, 20, and 40 min and 3, 6, 24, 48, and 72 hr after jet injection. The results indicated a rapid decrease in plasmid DNA concentration in the tumors. Jet injection of rhodamine-labeled DNA revealed that as early as 5 min after in vivo jet injection plasmid DNA appears in the cytoplasm and in the nuclei of tumor cells, indicating the rapid intracellular and nuclear entry of jet-injected plasmid DNA. Regarding systemic biodistribution, the highest amounts of plasmid DNA were detected in the blood 5 min after intratumoral jet injection, and rapidly dropped within 10 to 40 min. By comparison, only minimal amounts of plasmid DNA were detected in peripheral organs, which were cleared within 3 to 6 hr.